Radio Frequency IDentification (RFID) systems typically include RFID tags and RFID readers. RFID readers are also known as RFID reader/writers or RFID interrogators. RFID systems can be used in many ways for locating and identifying objects to which the tags are attached. RFID systems are particularly useful in product-related and service-related industries for tracking large numbers of objects being processed, inventoried, or handled. In such cases, an RFID tag is usually attached to an individual item, or to its package.
In principle, RFID techniques entail using an RFID reader to interrogate one or more RFID tags. The reader transmitting a Radio Frequency (RF) wave performs the interrogation. The RF wave is typically electromagnetic, at least in the far field. The RF wave can also be magnetic in the near field.
A tag that senses the interrogating RF wave responds by transmitting back another RF wave. The tag generates the transmitted back RF wave either originally, or by reflecting back a portion of the interrogating RF wave in a process known as backscatter. Backscatter may take place in a number of ways.
The reflected-back RF wave may further encode data stored internally in the tag, such as a number. The response is demodulated and decoded by the reader, which thereby identifies, counts, or otherwise interacts with the associated item. The decoded data can denote a serial number, a price, a date, a destination, other attribute(s), any combination of attributes, and so on.
An RFID tag typically includes an antenna system, a radio section, a power management section, and frequently a logical section, a memory, or both. In earlier RFID tags, the power management section included an energy storage device, such as a battery. RFID tags with an energy storage device are known as active or semi-active tags. Advances in semiconductor technology have miniaturized the electronics so much that an RFID tag can be powered solely by the RF signal it receives. Such RFID tags do not include an energy storage device, and are called passive tags.
It has been suggested that UHF RFID technology be used for tracking items within premises. Such premises include warehouses, stores, and other places where goods are handled. In particular, as further explained with reference to FIG. 6 of this document, it has been suggested that items can be tagged with RFID tags, and there can be RFID readers to read these tags. Upon so reading, the RFID readers can monitor the position of the tags, and therefore of the items, within the premises, or as they exit the premises. Such would substantially improve the internal operations of the premises, reducing operational costs, and resulting in savings that can be passed on to eventual consumers of the goods.
A problem arises upon recognizing that RFID readers installed at premises will be able to also read, in addition to tags of the items, tags that are foreign to the RFID environment of the premises. Such foreign tags are tags that may be carried by persons that come onto the premises for legitimate reasons, and can also be called personal tags. Such personal tags may have different functions. In some of the functions, such foreign tags can be unrelated to the operation of the premises, and yet such RFID readers at the premises could still be able to read the personal codes of these personal tags. This can confuse RFID-based Point-Of-Sale (POS) systems and Electronic Article Surveillance (EAS) systems.